Tin (Sn) has a specific charge capacity of about 1,000 mAh/gm in electrochemical applications, e.g., batteries. Current advanced, state-of-the-art Li-based batteries typically utilize carbon (C), i.e., graphite, as a negative electrode material having a charge capacity of about 372 mAh/gm. A great amount of research is being performed with the aim of increasing the charge capacity of batteries, with tin and silicon (Si) currently being candidates for use in advanced lithium (Li)-based batteries.
If the charge capacities of materials presently available for Li-based batteries were increased by a factor of two or more, manufacture of lighter batteries or batteries with larger charge profiles, or with longer service lifetimes would be facilitated. Such improvement in battery capacities would have a great impact in a multitude of technologies ranging from hand-held electronic devices, e.g., mobile phones, to space-based systems and vehicles. However, several problems are encountered with the use of Sn in Li-based batteries, including volume expansion due to intercalation of the Li. The result is an immediate and drastic reduction in the charge/discharge capacity after charging, as well as device failure.
Batteries containing materials comprising Li and Sn typically exhibit an immediate improvement vis-à-vis conventional Li-based batteries, but the improvement dissipates with use, i.e., over several charge/discharge cycles. Improvements in the performance of such materials in battery applications have been obtained by reducing the sizes of individual grains (i.e., particles). By reducing the particle size, the volume expansion upon intercalation can be diminished. Methods for reducing the size of Sn particles typically rely on a “top-down” approach in which larger particles are made smaller. The most common of these methods are mechanical, e.g., use of a ball mill for reducing the size of larger particles to achieve desired smaller particle sizes. Disadvantageously, however, such methods generally result in 0.5 micron or larger sized materials, with poor-to-moderate control over specific particle size. Often times, milling material abrades and contaminates the sample.
In view of the foregoing, there exists a need for improved approaches and methodologies for producing very small Sn particles, e.g., nano-sized particles, of specified particle size or range of sizes, suited for use in the development of improved electrochemical power sources, e.g., advanced Li-based batteries.